The present invention relates generally to metal spools such as those used for wire, and tools and methods of assembling such spools.
There are wide variety of spools available for carrying relatively heavy loads of wire, cable and the like. Spools for heavy load applications have traditionally been manufactured from such materials as sheet metal, plastic, wood, and cast iron. From the economic standpoint of material, transportation and assembly costs, it is particularly advantageous to provide such a spool made from sheet metal. Sheet metal has a characteristic of being relatively rigid while being relatively thin which allows the separate sheet metal components of the spool to be fabricated at a metal manufacturer, shipped closely together in large volume to a wire or cable manufacturer, and assembled at the plant of the wire or cable manufacture for receipt of wire or cable. Conventional sheet metal spools have been manufactured relatively inexpensively from either three-pieces or five-pieces of separate sheet metal components. It is also known to provide more complex sheet metal spools made from more pieces, however, more complex sheet metal spools diminish the economic cost advantages of three-piece and five-piece spools.
Five-piece spools typically comprise a cylindrical barrel upon which wire is wound, and a pair of two-piece flange sub assemblies disposed at respective ends of cylindrical barrel. Each flange sub assembly includes two pieces including a generally disc-shaped outer flange having a central opening, and a flange hub disposed in the opening and joined to the flange by a loose curl. Each flange sub assembly is secured to the cylindrical barrel by a tightened curl formed of closely interfitting curled metal edges of the flange hub, the flange and the cylindrical barrel. The tightened curl achieves a relatively rigid, high strength spool that is capable of carrying large loads of wire or cable and capable of being stacked and transported without falling apart or disassembling. Usually, the cylindrical barrel and the flange sub assembly are formed at the metal fabrication plant which allows the cylindrical barrels and flange sub assemblies to be shipped closely together thereby minimizing void space during transport. Then the final assembly of the cylindrical barrels to the flange sub assemblies occurs at the plant of the wire or cable manufacturer where wire or cable is subsequently wound onto the fully assembled spool.
One problem with prior five-piece metal spools is that the ability to transfer torque between different spool components of a fully assembled spool is relatively poor, particularly between the flange hub and the flange. The ability to transfer torque is highly desired for wire winding or pulling functions in which wire or cable is wound tightly onto the spool typically by applying a rotational force to drive holes in the central flange hub. For a fully assembled five piece spool having a 1 and {fraction (15/16)} inch diameter barrel, the tightened curl of the spool has typically only achieved between about 60 inch-lbs. and a maximum of about 100 inch-lbs. of torque load transfer (with a mean average of about 90 inch-lbs.) between the flange hub and the outer flange, using a test of applying a torque wrench to the flange hub through the drive holes while holding the outer flange fixed. However, in some applications, industry desires much higher torque load transfers between the flange hub and the outer flange, typically for wire winding or pulling functions, which makes prior five-piece metal spools insufficient for those applications.
To avoid torque load transfer problems associated with prior five-piece metal spools, industry has used three-piece metal spools in certain applications having a high torque load requirement. Three-piece metal spools typically comprise a cylindrical barrel upon which wire is wound, and a pair of flanges disposed at respective ends of cylindrical barrel. To connect the flanges to the cylindrical barrel, the cylindrical barrel includes tabs which are fit through punched out holes in the flanges. The tabs are crimped to the flanges to secure the flanges to the cylindrical barrel. Although the tab and hole mechanism provides sufficient torque transfer, three-piece spools have suffered from other strength disadvantages. More specifically, when three-piece spools carry heavy loads of wire or cable, the tabs tend to dislodge from the holes causing the flanges to pull away from the cylindrical barrel. This is especially problematic when stacking and transporting multiple three-piece spools loaded with wire or cable. The flanges of the three-piece spools can collapse under heavy loads which allows wire or cable to fall off the cylindrical barrel which in turn results in wasted wire or cable product.
It is therefore an object of the present invention to provide a practical die and practical method of assembling a metal spool that includes five-pieces which is capable of transmitting higher torque loads between the separate pieces of the spool as compared with that of the prior art.
In achieving the above objective, it is a further objective to provide a method of manufacturing a relatively inexpensive metal spool.
In accordance with these and other objectives, the present invention is directed towards a highly practical die and method for forming a formed metal curl with detents to assemble a metal spool and provide a high torque load transmissibility characteristic between the spool components. The spool is assembled from five pieces including a cylindrical barrel and a pair of flange sub assemblies in which each flange sub assembly includes an outer flange and an inner flange hub joined by a loose curl. The loose curl provides a smooth exposed curled surface on one side of the flange sub assembly and a circular curl entrance on the other side of the flange sub assembly. The cylindrical barrel includes circular edges at its opposing ends that are closely received into the circular curl entrances of the flange sub assemblies.
According to one of the aspects of the present invention, a method for forming a spool comprises the steps of first fitting the barrel into the two-piece flange sub assembly in such a way that the metal edge of the barrel fits into the curl entrance of the flange sub assembly. Then a stamping operation is applied to the loose curl, to first force the metal edge of the barrel through the curl entrance and to form it into the curl thereby securing the flange to the barrel and tightening the curl and then in the same operation form detents at a plurality of locations around the curl. Each detent extends through at least three external layers of the curl to thereby create a torque transmitting feature locking the two-piece flange sub assembly to the barrel.
According to another aspect of the present invention, a method for forming a spool comprises first arranging the flange sub assemblies on respective ends of the cylindrical barrel with respective circular ends of the cylindrical barrel being fitted into respective curl entrances. The flange sub assemblies and cylindrical barrel are also located between a pair of spaced apart dies. Each die includes a support housing, a curling member movable with respect to the support housing, a spring biasing the curling member away from the support housing, and a plurality of nibs carried by the support housing. The curling member has an annular curling face with the nibs being arranged in association with the curling face. The metal curls of the flange sub assemblies are also aligned in substantial diametric opposition with the respective annular curling faces of the dies. Finally, the flange sub assemblies and the cylindrical barrel are pressed between the dies. The step of pressing comprises two stages. During the first stage, the metal edges of the cylindrical barrel are curled into the respective curls with the annular curling face to secure the cylindrical barrel to the flange sub assemblies. During the second stage, a plurality detents are swaged into respective curls with the nibs projecting outward from the curling faces of the respective dies. The nibs project outward as the curling member of each die translates towards the support housing against the action of the spring.
According to another aspect of the present invention, a die for pressing one of the flange sub assemblies onto the cylindrical barrel to form a spool includes a body having an annular curling face that aligns in substantial diametric opposition with the loose curl of the flange sub assembly. The die presses the flange sub assembly on the spool with the curling face curling the edge of the cylindrical barrel radially outward to form a tightened curl which secures the flange sub assembly to the cylindrical barrel. The die also includes at least one and preferably a plurality of nibs arranged in association with the curling face. The nibs are moveable with respect to the curling face and project axially outward from the curling face and into the tightened curl during pressing operations to form corresponding detents in the tightened curl. The resulting detents provide increased torque transfer capacity between the flange sub assembly and the cylindrical barrel.
According to yet another aspect of the present invention, a die for forming a spool includes a support housing and a curling member that is adapted to move relative to the support housing. The curling member includes an annular curling face that aligns in substantial diametric opposition with the loose curl of the flange sub assembly. The curling member includes a plurality of slots extending through the curling face. The die further includes a plurality of nibs carried by the support housing and arranged in the slots in the curling face. A relatively heavy gauge spring is interposed between the curling member and the support member so as to bias the curling member away from the support housing. The die includes first and second pressing stages. During the first pressing stage, the die presses the flange sub assembly onto the cylindrical barrel with the curling face curling the circular edge of the cylindrical barrel radially outward into the curl to form a tightened curl that secures the flange sub assembly to the cylindrical barrel. During the second pressing stage, the curling member moves towards the support housing against the bias of the spring to expose the nibs. The nibs project outward from the curling face and into the tightened curl to form a plurality of dedents therein. The detents in the tightened curl provide increased torque transfer capacity between the cylindrical barrel and the flange sub assembly.
These and other aims, objectives, and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.